Intravenous heroin users comprise the second largest risk group of patients with the acquired immune deficiency syndrome (AIDS). In Western New York and Buffalo, heroin use has been recently increased to all time high. Although evidence of immune dysfunctions has been reported in parenteral heroin addicts with or without HIV infection, the molecular nature of these effects have not been clearly elucidated. Our laboratory was the first to report that several pure HIV proteins possess significant biological activities, and recreational drugs may act as co-factors in susceptibility to and progression of HIV infection. Among the early efforts, we were also the first to report that intravenous drug users, including heroin users, manifest low NK activity compared to matched control subjects. We further demonstrated that in vivo stereotaxic injection of HIV proteins plus excitatory amino acid agonists into the dorsal hippocampus of neonatal rat brains causes both gross and microscopic neuropathology. These interests merged in a series of preliminary studies demonstrating that heroin potentiates various neuro-immunopathogenic mechanisms mediated by HIV proteins. Thus, we hypothesize that heroin is a cofactor in the pathogenesis of HIV infection by acting in synergy with certain HIV proteins to affect the immune and central nervous systems of the infected host. Several experimental approaches will be used to determine the molecular mechanisms underlying the synergy between HIV proteins and heroin in HIV infected subjects. Lymphocyte and monocyte subsets from HIV1+ patients who are using heroin, who are not using heroin, seronegative heroin users, and normal donors will be cultured with HIV proteins +/- heroin to look for further modulation of various immune responses including dysregulation of cytokines/chemokines, upregulation of HIV entry coreceptors, neurotoxins (matrix metalloprotease-2 and-9 , nitric oxide, quinolinic acid) and apoptosis. Data will be stratified on the basis of HIV disease status, CD4 count, HIV viral RNA copy numbers and heroin use. The transmigration of infected monocyte/macrophages in to brain through the blood brain barrier may be facilitated by adhesion molecules and their respective ligands on endothelium and monocyte/macrophages. Human brain microvessel endothelial cells, several human CNS cell lines and primary astrocyte and neural progenitor cultures will be used to study the effects of heroin on adhesion molecules and neurotoxins. Neurotoxicity will be correlated with the neurotoxin production by treated monocytes, CNS cells and endothelial cells. Our preliminary studies show that heroin in synergy with HIV peptides demonstrate significant immunomodulatory effects on normal PBMC, CNS cells, and brain microvascular endothelial cells. Further studies will elucidate the molecular mechanisms underlying the immuno- and neuropathogenic effects of heroin use in HIV-l infection, and may yield novel therapies for the treatment of heroin using, HIV-infected patients.